1. Field of the Invention
The present invention relates to a process for preparing polyarylene thioether. More particularly, the present invention relates to a process which easily produces polyarylene thioether such as polyphenylene thioether, polyphenylene ether-thioether, polyphenylmethylenephenylene thioether, polyphenylethylenephenylene thioether, and the like under mild polymerization conditions at a low cost.
2. Description of Related Art
Hitherto, polyarylene thioether such as polyphenylene thioether is prepared by condensation polymerizing a dihalogenoaromatic compound with a sulfide of an alkali metal in a polar solvent at high temperature under high pressure. This process has various problems that (1) an alkali metal salt remains in the produced polyarylene thioether and deteriorates electrical properties of the polymer, and (2) since the polymerization is carried out at high temperature and high pressure, an amount of consumed energy is large so that a production cost is high.
Also, a process utilizing sulfuric acid as a catalyst is known. However, in this process, large amounts of by-products are produced, and a large amount of cross linked polymer is produced. As processes for preparing polyarylene thioether by using diphenyldisulfide and/or thiophenol are known from Japanese Patent Kokai Publication Nos. 213526/1988 and 213527/1988. These processes have drawbacks that expensive Lewis acid and an oxidizing agent are used in large amounts, and that diphenyldisulfide and thiophenol which are used as monomers are expensive.